Energy system contribution to 100-m and 2OO-m track running events

Transcription

1 Energy system contribution to 100-m and 2OO-m track running events R Duffield, B Dawson & C Goodman SchoOl of Human Movement and Exercise Science, The University of Western Australia, Crawley, Western Australia. While sprint track running events, lasting secs, are characterised by an anaerobic metabolic dominance, no actual track running data exist which have quantified the relative energy system contributions. Using previous methods employed by our laboratory, including 'in race' measures of V02, accumulated oxygen deficit (AOD), blood lactate concentration and estimated phosphocreatine degradation (La/PCr), the aerobic - anaerobic energy system contributions to 100-m and 200-m events were calculated. For the 100-m event, results indicated a relative aerobic - anaerobic energy system contribution (based on AOD measures) of 21%-79% and 25-75% for males and females respectively (9%-91% and 11%-89% based on La/PCr measures; p<0.05 for both genders for 100-m from AOD estimates). For the 200- m, a 28%-72% and 33%-67% contribution for male and female athletes was estimated (21%- 79% and 22%-78% based on La/PCr measures; NS from AOD estimates). A range of energy system contribution estimates for events of these durations have previously been proposed using a variety of techniques. The data from the current study also show different results depending on the measurement technique utilised. While AOD measures are often used to estimate anaerobic energy contribution, at such high exercise intensities (and brief exercise durations) as used in the present study, AOD measures showed larger aerobic energy estimates than expected. (J Sci Med Sport 2004;7:3: ) Introduction While extensive literature characterising the energetic involvement to high intensity exercise of 30 secs and less in duration exists 1, little applied research exists on the respective contribution of the energy systems in short duration, high intensity sporting events. Track running events 100-m and 200-m, spanning durations of 10 to 25 secs, are characterised as supra-maximal, highly anaerobic events 2. While the involvement of aerobic metabolism to events of such a short duration may be minimal, recent data have shown that the speed of the interaction of oxidative processes to the overall metabolic supply is faster than previously described 2. Despite an expectation that these events would be heavily dominated by energy supply from phosphocreatine breakdown and anaerobic glycolysis, as shown in Table 1, a wide range of predicted values have been reported for the respective energy system contribution to 100-m and 200-m events. Previous work by this laboratory a has quantified the relative metabolic demands of track running events from 400 m to 3000 m based on collection of'in-race' data. This current study aimed to extend that research by the calculation of relative aerobic and anaerobic 302

2 Energy system contribution to 100-m and 200-m... energy system contributions during actual 100-m and 200-m track running events. As Table 1 outlines, data on the relative energy system contribution in actual 100-m and 200-m events are sparse. However, several reports exist on the relative energy system contributions during laboratory-based cycle ergometer and treadmill exercise of similar durations. Problems associated with data collected via treadmill and cycle ergometry are the lack of specificity for both event and athlete. Generally, either the use of a cycle ergometer or use of a constant treadmill running velocity for a fixed time and/or a lack of specifically trained track athletes being used as subjects has limited the application of these findings to 100-m and 200-m track events. Recently, Spencer and Gastin 4 reported relative energy system contribution of trained track athletes to simulated 200-m events. V02 was measured during high-speed treadmill exercise to simulate the duration of the 200-m event while applying the Accumulated Oxygen Deficit (AOD) measures of Medbo et al 5 to calculate the anaerobic energy contribution. Ward-Smith 6 and Peronnet and Thibault 7 have applied mathematical models of running in order to predict the respective aerobic and anaerobic energy involvement for these events. These procedures have been based on satisfying the first law of thermodynamics and have substituted physiological data where appropriate to estimate the energetic contribution of the metabolic pathways to 100-m and 200-m events. While no measured data exist detailing the contribution of the respective metabolic pathways involved in actual 100-m and 200-m track events, Hirvonen et al8,9 reported changes in muscle ATP, PCr and lactate ([La-lm) following completion of 40-m to 100-m sprints and at 100-m intervals of a 400- m track event respectively. While ~'O 2 was not measured, based on the reported changes in metabolic substrates it is possible to calculate the anaerobic yield and then convert the calculated anaerobic ATP yield into 02 equivalents (ml.kg-1) 1. From the data of Hirvonen et al8, an anaerobic yield for the 100 m is calculated Source Event Aerobic Anaerobic Measurement contribution contribution Serresse et al s 3 97 Cycle ergo - VO 2 measured ATP-PCr and glycolysis estimated Ward-Smith m 7 93 Mathematical modelling Peronnet and Thibault m Mathematical modelling Bogdanis et al s Cycle ergo-biopsy measures Ward-Smith m Mathematical modelling Peronnet and Thibault m Mathematical modelling Bogdanis et al s Cycle ergo-biopsy measures Calbert et al s Cycle ergometer - AOD Withers et al s Cycle ergometer - AOD Spencer and Gastin m Treadmill - AOD Note: AOD - accumulated oxygen deficit. Table 1: Relative % aerobic- anaerobic contribution to 100-m and 200-m track events and measurement methods used. 303

3 Energy system contribution to lo0-m and 200-m... Event N Gender Age Height Mass Est. Muscle Peak V02 (y) (cm) (kg) Mass (kg) 1 (ml-kg'l-min d) lo0-m 9 M (±4.5) (+5.6) (±7.36) (±6.57) (±6.18) lo0-m 6 F 24, , (±5.1) (±5,4) (±2.87) (±4,29) {+_4.43) 200-m 8 M {±4.4) (±4,9) (±6.31) (±6.59) (±4.31) 200-m 5 F (±5.7) (±6.0) (±1.69) (±1.26) (±4.38) 1 Calculated according to Martin et al. 11. Table 2: Descriptive characteristics of subjects (mean±sd). as 19.9 ml 02 eq'kg -1, while a calculated anaerobic yield from the data of Hirvonen et al 9 for the first 100 m of a 400-m event is 12.4 ml 02 eq,kg -1 and for the first 200 m, 20.2 ml 02 eq, kg -1. The reported post-run [La-lm concentration was the main source of difference between the respective 100-m measures, with a greater value reported for the all-out 100-m run 8. Hence, the aim of the current study was to quantify the relative aerobic and anaerobic energy system contribution to 100-m and 200-m track running events. Based on previous methods used by this laboratory to measure energy system contributions to 400, 800, 1500 and 3000-m events, 'in race' data collection of VO 2, AOD, blood lactate concentration ([La-] b) and estimated phosphocreatine (PCr) degradation was utilised to calculate the respective aerobic and anaerobic energy involvement. MethodS Subjects Trained male (n= 9) and female (n= 6) 100-m and male (n= 8) and female (n= 5) 200-m track athletes (descriptive characteristics are presented in Table 2) volunteered for this study. All subjects gave their written consent prior to engaging in any testing procedures. Subjects ranged in ability from Club/ State-level (100-m n= 10, 200-m n= 9) to National-level (100-m, n= 5, 200-m, n= 5)'athletes. Testing was performed both in the Exercise Physiology Laboratory at the School of Human Movement and Exercise Science, The University of Western Australia (UWA), and on an outdoor synthetic rubber (Rekortan) 400-m athletic track. Human rights approval was granted prior to the commencement of the study by the Human Ethics Committee of UWA. Procedure overview All subjects performed four testing sessions, separated by at least 48 hrs and no more than seven days, with time of day kept constant between testing sessions for each participant. Following initial familiarisation (test 1) with both the exercise protocol and Cosmed K4b 2 portable gas analysis system, a second testing session involved a graded incremental (motorised) treadmill step test and a run to volitional exhaustion. Included in this session were anthro- 304

4 Energy system contribution to 100-m and 200-m... pometric measures for the estimation of muscle mass 11, consisting of body mass, height, forearm, thigh and calf girths and thigh and calf skinfolds. The final two testing sessions involved participants performing a time trial run over their chosen athletic distance (either 100 m or 200 m) on an outdoor 400-m synthetic athletic track. Subjects were asked to refrain from the ingestion of food or caffeine 2-3 hrs prior to all testing sessions and from engaging in physical exercise in the 24 hrs prior to testing. All testing took place during the competition phase of the local athletic season. Outdoor track testing sessions were postponed if climatic conditions were too extreme (40 C < Temp <15 C, wind >4m.s -] or raining). Graded exercise test (G}(T) Following a standardised warm-up of 5-min treadmill running (9-10 km.h d) and a 5-min stretching period, subjects performed 5-6 steps of 4-5-min duration, separated by recovery periods of 4-6 mins 4. The treadmill was maintained at a constant 1% gradient in order to account for the energy cost involved in over-ground running 12, with initial velocities of 9-10 km.h -1 and final velocities of km.h -1 (40-95% peak "VO2). During the exercise test, expired air was analysed with a breath-by-breath Cosmed K4b 2 portable gas analyser (Rome, Italy). Calibration of the Cosmed turbine with a 3 L syringe and gas analysers with an alpha verified beta calibration gas (BOC gases, Perth, Australia) both occurred in line with manufacturer's instructions at the commencement of each individual step of the GXT. Following the completion of the warm-up and initial calibration procedures, the Polar Heart rate monitor (Finland) and Cosmed K4b 2 base harness were arranged on the subject and the Cosmed K4b 2 system attached to the subject's torso. Subjects then stepped on to the moving belt of the treadmill at the selected initial speed. At the completion of the step, the treadmill was stopped, Cosmed K4b 2 measurement was ceased and re-calibration procedures (as previously mentioned) were conducted prior to the commencement of the next step. Following completion of the final step, subjects were allowed a recovery period of mins before completing an incremental run to volitional exhaustion in order to elicit peak VO 2. This run began at the penultimate treadmill velocity achieved by the subject during the previous step test and increased by 1 km.h -1 each minute until the subject reached volitional exhaustion. Peak VO2 was attained when the subject could not continue with the exercise test and an average of the highest values attained over any oneminute period was used as the peak "VO 2 value. Track sessions On arrival, subjects engaged in a standardised warm-up consisting of several laps jogging, 20 mins stretching and 4x m "run-throughs" at increasing speeds. Following stretching, the Polar Heart rate monitor and Cosmed K4b 2 base harness were arranged on the subject and the Cosmed K4b 2 system attached to the subject's torso. Subjects then performed the run-throughs before calibration procedures were employed (as previously described for GXT). Before commencement of the time trial, a pre-race capillary blood sample from an ear lobe was obtained for the measurement of [La-] b (Accusport blood lactate analyser, Boehringer Mannheim, Germany). Once prepared, measurement of 305

5 Energy system contribution to 100-m and 200-m... VO2 commenced, following which subjects proceeded to the start line. The period from the commencement of Cosmed K4b 2 measurement to the start of the run was timed in order to locate the exact start of the time trial on the data file. Prior to commencement of the trial, subjects were given standard instructions pertaining to the need for maximal effort throughout the trial. At the start line, subjects were given the standard starting commands, at which point they approached the start line and then began the time trial. Electronic infra-red timing systems (customised system, School of HM and ES, UWA) were located at the respective start lines (100 m and 200 m) and common finish line, and movement of the subject through the starting infra-red beam initiated the timing mechanism. The timing system enabled the measurement of times and calculation of speed for both the 100-m trial and each 100-m of the 200-m trial. Following completion of the time trial, Cosmed K4b 2 measurement was ceased and 1, 3, 5 and 7-min capillary blood samples from the ear lobe were obtained for the measurement of post exercise [La-] b. Finally, the Cosmed K4b 2 system was then detached from the subject and a gentle cool-down was allowed. Calculation of relative energy expenditure GXT For each subject, steady state (breath-by-breath) VO2 data were averaged over the final minute of each step (Excel 10.0). Pinnington et ap 3 have previously reported increased Cosmed K4b 2 measures of "QO 2 when compared to a laboratory metabolic cart. Hence, prior to analysis, Cosmed K4b 2 VO2 data were corrected using regression equations that were calculated based on recent research conducted in our laboratory.using high intensity 1, 3 and 10-rain treadmill runs [regression equation: VO2= * Cosmed ~'O , r 2= 0.84]. A linear regression analysis was used on the collected step test data to determine the individual VO2-velocity relationship for each subject, using custom written AOD determination software (Labview 5.1 National Instruments). This analysis allowed for the measurement of AOD for each time trial from calculating the difference between the predicted "QO2 for the respective speed (from extrapolation of the calculated relationship) and the measured VO2. Track session For each subject, data from the fastest time trial were used in subsequent analysis. Cosmed K4b 2 breath-by-breath data were aligned to run start time in order to.exclude data that were not collected during the time trial. The 100-m spl!t times, obtained from the electronic timing system, allowed the calculation of VO 2 consumed during each 100-m portion of the event. As Cosmed K4b 2 software reports VO2 data each breath in ml*min -], an average VO2 was calculated based on all breaths collected during each individual 100-m segment (Excel 10.0). This was then converted into a total VO 2 (L) consumed for each 100-m based on the respective time taken to complete the 100-m split. Based on the individual VO2 - velocity relationship determined from the graded step test, corrected "QO2, speed and time were used to calculate the AOD of each 100-m component of the race (using custom written AOD determination software, Labview 5.1 National Instruments). This allowed for a measurement of an aerobic and anaerobic energy contribution to each 100 m throughout the 306

6 Energy system contribution to lo0-m and 200-m... time and a total contribution over the whole run. Gastin 2 provides support for the application of AOD methodology to non-constant maximal exercise, demonstrating no differences in the calculation of AOD between all-out supramaximal and constant intensity exercise. Accumulated [La-] b and estimated PCr degradation, in conjunction with AOD measures, were used as a secondary method to determine anaerobic energy contribution based on data collected during the track-based time trial. Glycolytic energy contribution based on [La-] b accumulation was calculated according to di Prampero 14 as 3.0 ml 02 equivilents*kg -1 body mass for each 1 mmolo1-1 increase above pre-exercise levels. Phosphocreatine store contribution was calculated as 37.0 ml O2.kg -1 muscle mass 14. Muscle mass was estimated based on forearm, thigh and calf girths and skinfolds 11. Therefore, a second measure of anaerobic energy contribution (AOD being the first) was obtained by the addition of ml 02 eq*kg -1 determined from [La-] b and PCr stores respectively. Percentage anaerobic (and aerobic) energy contribution to each event was calculated as the total estimated anaerobic energy output divided by the total energy utilised during the event. This calculation was conducted for both AOD measures and also the La/PCr measure of anaerobic energy supply. Statistical analysis Comparison across event distance and gender was analysed by a two-way ANOVA (event x gender), with post-hoc analysis performed using Tukey tests where necessary. Within-event comparison of total anaerobic energy expenditure and relative anaerobic percentage contribution based on methodology used were analysed by a one-way ANOVA. Relationships between event performance and measured parameters were analysed by a Pearson's correlation coefficient. Significance was set a priori at the 0.05 level and all statistical analysis was conducted on SPSS statistical software (Version 10). Results Mean (_+SD) and range of values for the aerobic and anaerobic contribution to 100-m and 200-m track races calculated by both AOD and La/PCr methods are presented in Table 3. Mean (_+SD) values for race time, peak heart rate, peak race V02, peak [La-]b, AOD, La/PCr anaerobic total, energy cost and average speed for 100-m and 200-m events respectively are presented in Table 4. ANOVA results revealed significant differences (p<0.05) between 100-m and 200-m events for male athletes in the % anaerobic energy contribution (La/PCr), with larger values recorded in the 200-m trial (Table 3). No significant differences (p>0.05), as a result of gender, in the anaerobic energy contribution were noted for either event. However, males tended to show a greater anaerobic energy involvement in both the 100 m and 200 m (Table 3). Significant differences (p<0.05) were revealed in the total energy cost of the 100-m trial between male and female athletes, with larger energy costs recorded for male athletes. Also, male peak race VO 2 and % peak V02 were significantly larger in the 200-m than 100-m event (p<0.05). No significant differences (p>0.05) were revealed between 100-m and 200-m events for AOD, % anaerobic energy contribution (AOD), peak [La-] b, anaerobic energy total (La/PCr) (Table 4) or peak ~O 2 for either gender. Differences were evident between the measurement techniques for the 307

7 Energy system contribution to lo0-m and 200-m... AOD La/PCr Event % aerobic % anaerobic % aerobic % anaerobic lo0-m Male " (_+7.9) (_+7.9) (_+3.3) (_+3.3) (13-35) (65-87) (6-14) (86-94) Female " (-+7.4) (_+7.4) (_+5.8) (+-5.8) (17-33) (67-83) (6-19) (81-94) 200,m Male # (_+7.9) (_+7.9) (-+8.5) (_+8.5) (17-40) (60-83) (14-35) (65-86) Female (_+8.0) (_+8.0) (-+7.7) (_+7.7) (26-45) (55-74) (15-28) (72-85) * Significantly different (p<0.05) to AOD measures. # Significantly different (p<0.05) to male 100-m. Table 3- Mean (_+SD) and range of values calculated by AOD (accumulated oxygen deficit) and La/PCr methods for the relative aerobic and anaerobic energy contribution to both male (11 =9 and 8) and female (n = 6 and 5) lo0-m and 200-m trials. lo0m Male 200m Male loom Female 200m Female Race time (s) * # (-+0.4) (+_1.1) (+_0.5) (+_1.2) Peak race VO~ " (ml.kg-l.min-7) (+_8.53) (+7.31) (_+7.04) ( ) % peakvo * (-+12.9) (+_13.2) (-+18.3) (+_27.5) Peak race HR (bpm) (+10) (-+11) (-+11) (-+11) % HR max (_+5) (+-4) (_+1) (_+1) Peak [La-] b (mmol.r 1) (_+1.5) (_+3.0) (_+1.7) (_+2.3) Race AOD (ml 02eq.kg "1) (_+4.4) (_+3.7) (_+2.9) (v3.0) La/PCr anaerobic total (mr O2eq.kg 1) (_+5.1} (_+9.4) (+5.2) (-+7.4) Total Energy Cost " (ml 02.kg'~i.m "1) (_+0.046) (+_0.012) (_+0.035) (v0.014) Speed(m.s 1} (_+0.2) (_+0.4) (-+0.3) (-+0.5) * Significantly different (p<o.05) to lo0-m male. # Significantly different (p<0.05) to lo0-m female. Table 4: Mean (-+SD) values for race time, peak race VO 2, % peak V02, peak race heart rate, % max heart rate, peak blood lactate, accumulated oxygen deficit (AOD), La/PCr anaerobic total, total energy cost and average speed for male (/1=9 and 8) and female (n= 6 and 5) I00-m and 200-m trials respectively. 308

8 Energy system contribution to 100-m and 200-m... calculated relative anaerobic energy contribution to the 100-m event in both genders, with AOD estimates significantly less (p<0.05) than La/PCr measures. While no significant differences were noted between AOD and La/PCr measures of anaerobic energy contribution for the 200-m trial, p values approached significance (p= 0.08 and 0.06 for males and females respectively). In conjunction, weak to moderate, non-significant (p>0.05) correlations between AOD and La/PCr measures of anaerobic involvement were noted (r= 0.60, 0.10 and 0.53, 0.37 for male and female 100-m and 200-m respectively). No significant correlations (p>0 05) were found between either 100-m or 200- m performance and peak race VO2, AOD, % anaerobic energy contribution (AOD) (except female 200-m), peak [La-] b, anaerobic energy total (La/PCr) or % anaerobic energy contribution (La/PCr) for either gender. A strong (p<0.05) correlation between the energy cost and male 200-m performance (r= 0.85) was recorded. A moderate correlation (near significance, p= 0.06) between energy cost and the male 100-m trial (r= 0.64) was also noted. Finally, anaerobic energy contribution calculated from AOD measures showed a strong negative correlation to race performance for female 200-m runs (r= -0.96, p<0.01). DiSCUSSiOn While sprint track events are heavily reliant upon anaerobic metabolism s, the actual quantification from measured physiological data of the respective energy pathway involvement in these events, particularly during track running, is non existent. This current study aimed to extend previous methods of in-race data collection 3 to calculate the relative aerobic and anaerobic energy system contribution to 100-m and 200-m track running. Results indicated a significant difference (p<0.05) between measurement techniques of anaerobic metabolism for the 100-m, with the anaerobic energy contribution estimated as 79% and 75% for male and female athletes from AOD measures while La/PCr estimates calculated a 92% and 89% contribution. For the 200-m event AOD anaerobic energy contribution was 72% and 67% while La/PCr estimates indicated an 80% and 78% role (male and female respectively; NS between methods). Previous research is varied in both the applications of methodologies to measure anaerobic metabolism and the results derived from such measures. While mathematical modelling has outlined a very low role of aerobic metabolism in both 100-m (4-8%) and 200-m events (8-4%) 6,7, measured physiological data, particularly for the 200-m event (both treadmill and 30-sec cycle ergometer efforts), record a greater oxidative role (28% +) (see Table 1). As differences in results obtained from the respective measurement techniques exist in the present research, the data from our current study conform to estimates from both measured and predicted research data. Estimates based on La/PCr measures from the current study show similarities to the mathematical modelling results of Ward-Smith 6, Peronnet and Thibault 7 and Withers et ap 5, in that the anaerobic energy contribution to 100-m and 200-m events is estimated as around or above 90% and 80% respectively. Conversley, AOD data from the present study show almost identical results for the anaerobic energy contribution to 200-m events as Spencer and Gastin 4 reported, indicating a comparatively increased role of oxidative metabolism (200-m; 71% anaerobic). Other data collected from maximal exercise of 10 secs duration have shown a 97% anaerobic energy dominance 16, while 200-m (20 309

9 Energy system contribution to lo0-m and 200-m... sec +) and 30-sec duration exercise has been reported as being between 8-42% anaerobic (Table 1). While the ability of the athlete, performance effort and measurement method used will alter the final estimation of the respective anaerobic contribution, such a large variance in estimated anaerobic energy contribution makes quantifying the energetics of the events and associated planning of training programs difficult. Anaerobic yields (ml 02 eq'kg -1} calculated from the reported changes in ATP, PCr and [La-] m (assuming 25% active muscle mass 5) showed similarities with the present AOD anaerobic yield for 100-m and 200-m events 8,9. The calculated anaerobic yield for a 100-m sprint of 19.9 ml 02 eq.kg-]8 and first 200-m of a 400-m, eq ml.kg -19 were similar to the AOD values calculated here of 17.4 and 28.4 ml 02 eq kg -1 respectively. In contrast, a greater discrepancy is seen when comparing the anaerobic yield values calculated from La/PCr measures of 45.9 and 52.6 ml 02 eqokg -1 (100-m and 200-m respectively). A problem associated with the quantification of energy system involvement in events of such short duration is obtaining an accurate measurement, particularly of the involvement of the anaerobic energy systems. While AOD measures based on the linear extrapolation of sub-maximal 02 demands have become popular tbr estimating anaerobic energy system involvement, this method is not without criticism 1. In particular, the prediction of the oxygen demand at supra-maximal exercise intensities based on sub-maximal exercise, assumes that the relationship between exercise intensity and oxygen demand remains linear beyond maximal exercise. Breaches of this assumption have previously been demonstrated 17, with greater efficiencies reported at submaximal compared to supra-maximal exercise intensities. Hence, the accurate application of AOD measures to 100-m and 200-m events, or the prediction of the 02 demand for very short duration exercise at very high intensities (potentially % VO 2 max) from a plot of sub-maximal data, is in doubt. Due to changes in the mechanical efficiency in running as the intensity increases, AOD measures have been reported to underestimate the anaerobic energy contribution 17. Accordingly, the anaerobic energy contributions calculated from AOD measures in the present research are comparatively lower than expected for events of such a short duration. However, they do show similarities to the anaerobic yield calculated from direct muscle metabolite measures 8,9. Anaerobic energy contribution estimates based on La/PCr methods appear similar to data published over similar time frames (see Table 1). Also (accounting for the differences in exercise duration), La/PCr calculations show similarities to the anaerobic contributions calculated from muscle metabolite data in 10- and 20-sec maximal efforts of 87% and 82% respectively 1. However, flaws in the use of [La-] b as a quantifiable measure of anaerobic metabolism are also well documented 2. Hence, the difficulties that arise in the measurement of anaerobic energy ~ontributions in maximal but non-exhaustive exercise of such a short duration again limit the precise estimation of the relative energy system involvement. Previously Hill et alls have reported the use of a Non Linear Regression model, based on measures of accumulated VO2, velocity and time, to predict 310

10 Energy system contribution to lo0-m and 200-m... the 02 demand and the AOD of supra-maximal exercise. Based on repeated trials of exhaustive exercise at different supra-maxtmal intensities, Hill et a118 used iterative non-linear functioning to predict the 02 demand and AOD without the extrapolation of 02 demand from sub-maximal workloads. While we attempted to utilise this method in the current study, the lack of similarity between intra-subject trials due to differing environmental conditions (wind, temperature) and hence differences in performance between trials resulted in unrealistically high AOD values (range = ml 02 eq). However, future research and methodological adjustments may yet successfully apply Hill et al's ~8 concept to measure AOD in high intensity, short duration exercise. Gastin 2, in a summary analysis of research on the interaction of the respective energy systems, has estimated a 94%-6% anaerobic-aerobic contribution to 10 secs of exhaustive exercise. By 20 secs the respective reliance has shifted to an 82%-18% split, which fits with results based on La/PCr estimates of anaerobic energy system involvement in the present study. Gastin 2 also outlined a crossover point (between secs) during an exercise bout where aerobic metabolism becomes the predominant source of ATP supply. While Spencer and Gastin 4 and previous research from our laboratory a have supported this finding, as the duration of the current events investigated were secs and secs respectively, the duration of the runs were insufficient to see a dominant response of the oxidative energy system. While no data exist outlining the energy cost (EC) of 100-m and 200-m track events from measured physiological data, previous work by Lacour et a119, Hill et ap 8 and recently from our laboratory 3 has estimated the EC of the 400-m event. Estimates of ml kg-l.m -1 have been reported by both Hill et al ]8 and Duffield et al3, while Lacour et all9, probably due to a higher calibre of athlete, estimated an EC of mlokg-l.m -1. All three studies have shown a corresponding increase in the EC as the intensity of the exercise increases and distance is reduced. While the current 100- to 200-m male data fit this trend for an increased EC (0.218 and ml kg-l.m -1 respectively), the 200-m EC is lower than 400-m data reported for athletes of a similar ability a. Speculative reasons for this irregularity may be the higher [La-]b accumulation in the 400- m event, causing a comparatively greater level of muscular fatigue and hence a decreased efficiency in the 400-m event (resulting in a higher EC than the 200- m event). Female 100-m and 200-m EC were almost identical, with the EC for the 200-m event slightly greater than the 100-m event (0.169 and ml kg- 1 m-1 respectively). Again, speculation as to why this was the case may possibly involve the comparatively limited opportunity for involvement of oxidative metabolism during the 100-m as compared to the 200-m event. Despite the concerns previously raised regarding the validity of applying AOD methodology to exercise of such a high intensity and short duration, anaerobic energy contribution calculated from AOD measures did correlate strongly to female 200-m performance. Anaerobic energy contributions showed a strong correlation with faster 200-m performance for female athletes. However this finding was not replicated in the 100-m event nor for 100-m or 200-m male events. Other significant correlations included moderate to strong correlations between EC and male 100-m and 200-m performance. However this can be explained as a result of race time, as the longer the duration of the event the 311

11 Energy system contribution to 100-m and 200-m... greater the amount of energy supplied. In conclusion, the current study determined the relative aerobic-anaerobic energy system contribution (based on the AOD method, for male and female athletes) as 21%-79% and 25%-75% for 1O0-m track events and 28%-72% and 33%-67% for 20O-m events. In comparison, the calculated relative anaerobic contribution from La/PCr measures showed a greater anaerobic energy system contribution. While these estimates were based on data measured during actual 1O0-m and 200-m track events, the limitations involved in the application of methods of estimating the involvement of anaerobic metabolism partially restrict the accuracy of these findings. While this research is the first actually to measure the energetics during actual track events of these distances and awaits further confirmation, the data obtained here for AOD and La/PCr estimates respectively are consistent with estimates based on previous laboratory findings and mathematical modelling of such athletic events. References 1. Bogdanis GC, Nevill ME, Lakomy HKA et al. Power output and muscle metabolism during and following recovery from 10 and 20 s of maximal sprint exercise in humans. Acta Physio Scand.1998; 163: Gastin PB. Energy system interaction and relative contribution during maximal exercise. Sports Med.2001; 31{10): Duffield R, Dawson B and Goodman C. Energy system contribution to 400 m and 800 m track running. J Sports Sci.2004; In press. 4. Spencer MR and Gastin PB. Energy system contribution during 200 to 1500m running in highly trained athletes. Med Sci SporExe.2001; 33(1): Medbo JI, Mohn AC, Tabata I et al. Anaerobic capacity determined by maximal accumulated 02 deficit. J Appl Physiol. 1988; 64: Ward-Smith AJ. A mathematical theory of running, based on the first law of thermodynamics, and its application to the performance of world-class athletes. J.Biom. 1985; 18(5): Peronnet F and Thibault G. Mathematical analysis of running performance and world records. J App Physiol. 1989; 67(1): Hirvonen J, Rehunen S, Rusko H et al. Breakdown of high energy phosphate compounds and lactate accumulation dui:ing short supra-maximal exercise. Eur J Appl Physiol. 1987; 56: Hirvonen J, Nummela A, Rusko H et al. Fatigue and changes of ATP, creatine phosphate and lactate during the 400-m sprint. Can JAppl Physiol. 1992; 17(2): Bangsbo J, Michalsik L and Peterson A. Accumulated 02 deficit during intense exercise and muscle characteristics of elite athletes. Int J Spor Med. 1993; 14(4): Martin AD, Spenst LF, Drinkwater DT et al. Anthropometric estimation of muscle mass in men. Med Sci Spor Ex. 1990; 22: Jones AM and Doust JH. A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. J Spor Sci. 1996; 14: Pinnington HC, Wong P, Tay Jet al. The level of accuracy and agreement in measures of FeO 2, FeCO 2, and d E between a Cosmed K4b 2 portable respiratory gas analysis system and a metabolic cart. J Sci Med Spot.2001; 4(3): di Prampero PE. Energetics of muscular exercise. Rev Physiol, Biochem Pharm. 1981; 89: i Withers RT, Sherman WM, Clark DG et al. Muscle metabolism during 30, 60 and 90 s of maximal cycling On an air-braked ergometer. Eur J Appl Physiol. 1991; 63: Serresse O, Lortie G, Bouchard C et al. Estimation of the contribution of the various energy systems during maximal work of short duration. Int J Spor Med. 1988; 9(6): Luhtanen P, Rahkilia P, Rusko H et al. Mechanical work and efficiency in treadmill running at aerobic and anaerobic thresholds. Acta Physiol Scand. 1990; 139: Hill DW, Ferguson CS and Ehler KL. An alternative to determine maximal accumulated 02 deficit in runners. EurJAppl Physiol.1998; 79:

12 Energy system contribution to lo0-m and 200-m Lacour JR, Padilla-Magunacelaya.S., Barthelemy.J.C et al. The energetics of middle distance running. Eur J Appl Physiol Occup Physiol. 1990; 60( 1): Calbert JAL, Chavarren J and Dorado C. Fractional use of anaerobic capacity during a 30- and a 45-s wingate test. EurJAppl Physiol.1997; 76: